The present invention relates to the pressing of doughballs into flat shapes, such as, for example, tortillas. More particularly, the present invention relates to a method and apparatus for controlling the operation of a mechanical press employed for forming doughballs into tortillas.
Machines for the commercial production of tortillas from doughballs are well known. One such machine is shown and described in U.S. Pat. No. 4,668,524, granted May 26, 1987 to the inventor hereof and assigned to the assignee of this patent application. In the machine described in this patent, doughballs are magazine-fed onto a conveyor belt that is indexed in sequence with the operation of a reciprocably movable plate of a mechanical press to force the doughballs between the movable plate and the fixed plate of such press into the flattened tortilla shapes.
It is desirable in the commercial production of tortillas that they undergo a degree of parbaking during the pressing operation. Accordingly, the press plates are heated to an elevated temperature by electrical heating elements carried thereby. In order to effectively transmit heat from the fixed plate to the pressed dough shells for parbaking purposes, however, the thickness of the conveyor belt must be minimal, typically about .010 inches (10 mils) thick. Also, in order to prevent sticking of the flattened dough to the belt and to obtain effective discharge of the finished product from the belt, the belts have typically been formed of teflon-coated fiberglass material. Both of these characteristics render the belts susceptible to damage.
Moreover, in the operation of the described prior art machine it is desirable that the movable plate be capable of operating continuously, regardless of the existence of doughballs between the plates when the plate is activated downwardly. However, it has been found that the thin conveyor belts in existing equipment deteriorate rapidly due primarily to the fact that particulate material such as dough particles can migrate between the belt and the fixed plate and there can become hardened due to pressure applied by the plates and to heat by the heating elements. Thus, when, during the absence of doughballs on the belt, the plates are brought together, the hardened particles impact the belt to the point, in the most severe case, of penetrating the belt thickness. Holes produced in the belt in this manner propagate rapidly resulting in the need to change belts frequently.
It is accordingly to the amelioration of the above described problem that the present invention is directed.